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A273630
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a(n) = Sum_{k = 0..n} (-1)^k*k^3*binomial(n,k)^3.
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3
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0, -1, 0, 162, 0, -11250, 0, 576240, 0, -25259850, 0, 1007242236, 0, -37685439792, 0, 1346871240000, 0, -46504059326010, 0, 1562983866658500, 0, -51407781284599740, 0, 1661123953798807680, 0, -52886433789393750000, 0, 1662782404368229351200
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OFFSET
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0,4
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COMMENTS
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Let d(n) = Sum_{k = 0..n} (-1)^k*binomial(n,k)^3. Clearly, by symmetry of the binomial coefficients we have d(2*n + 1) = 0. Dixon's identity is the result d(2*n) = (-1)^n*(3*n)!/n!^3. A generalization is: for r a nonnegative integer there holds Sum_{k = 0..n} (-1)^k*binomial(k,r)^3*binomial(n,k)^3 = (-1)^r*binomial(n,r)^3*d(n - r). This is the case r = 1. See A273631 (case r = 2) and A245086 (case r = 0).
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LINKS
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Table of n, a(n) for n=0..27.
P. Bala, A generalization of Dixon's identity
J. Ward, 100 Years of Dixon's Identity, Irish Mathematical Society Bulletin 27, 46-54, 1991
Wikipedia, Dixon's identity
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FORMULA
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a(2*n) = 0; a(2*n + 1) = (-1)^(n+1)*(2*n + 1)^3*(3*n)!/n!^3.
a(2*n + 1) = -(2*n + 1)^3*A245086(2*n) = (-1)^(n+1)* (2*n + 1)^3*A006480(n).
a(n) = Sum_{k = 1..n} (-1)^k*multinomial(n, 1, k - 1, n - k)^3.
Recurrence: a(n) = -3*n^3*(3*n - 5)*(3*n - 7)/((n - 1)^2*(n - 2)^3) * a(n-2).
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MAPLE
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seq(add((-1)^k*k^3*binomial(n, k)^3, k = 0..n), n = 0..30);
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MATHEMATICA
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Table[Sum[(-1)^k*k^3 Binomial[n, k]^3, {k, 0, n}], {n, 0, 27}] (* Michael De Vlieger, Jul 22 2016 *)
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PROG
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(PARI) a(n) = sum(k=0, n, (-1)^k*k^3*binomial(n, k)^3) \\ Felix Fröhlich, Jul 22 2016
(MAGMA) [&+[(-1)^k*k^3 *Binomial(n, k)^3: k in [0..n]]: n in [0..70]]; // Vincenzo Librandi, Jul 23 2016
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CROSSREFS
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Cf. A006480, A245086, A273631.
Sequence in context: A232308 A232458 A214164 * A118470 A081724 A025374
Adjacent sequences: A273627 A273628 A273629 * A273631 A273632 A273633
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KEYWORD
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sign,easy
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AUTHOR
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Peter Bala, Jul 17 2016
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STATUS
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approved
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